The present invention was made in the course of developing improvements in polyester fiberfill. Polyester fiberfill filling material is sometimes referred to as polyester fiberfill and has become well accepted as a reasonably inexpensive filling and/or insulating material especially for pillows, and also for cushions and other furnishing materials, including other bedding materials, such as sleeping bags, mattress pads, quilts and comforters and including duvets, and in apparel, such as parkas and other insulated articles of apparel, because of its bulk filling power, aesthetic qualities and various advantages over other filling materials, so is now manufactured and used in large quantities commercially.
Polyester fibers with longitudinal voids have generally been preferred for use as filling fibers over solid filaments, and improvements in our ability to make such polyester fiberfill with a round periphery has been an important reason for the commercial acceptance of polyester fiberfill as a preferred filling material. Examples of fiber cross-sections with longitudinal voids are those with a single void, such as disclosed by Tolliver, U.S. Pat. No. 3,772,137, and by Glanzstoff, GB 1,168,759, 4-hole, such as disclosed in EPA 2 67,684 (Jones and Kohli), and 7-hole, disclosed by Broaddus, U.S. Pat. No. 5,104,725, all of which have been used commercially as hollow polyester fiberfill filling material. Most commercial filling material has been used in the form of cut fibers (often referred to as staple) but some filling material, including polyester fiberfill filling material, has been used in the form of deregistered tows of continuous filaments, as disclosed, for example by Watson, U.S. Pat. Nos. 3,952,134, and 3,328,850.
We use herein both terms "fiber" and "filament" inclusively without intending use of one term to exclude the other.
Practically all of the polyester fiber that has been manufactured commercially hitherto has been based on ethylene glycol (2G) and on terephthalic acid (T), and ethylene terephthalate polymers have sometimes been referred to as 2G-T, accordingly. Such polyesters have been preferred because of cost and availability, but others have been mentioned in the literature, such as 3G-T (sometimes referred to as PTT) and 4G-T for example. The present invention is not limited to fibers of 2G-T polyesters, but may be applied to other glycol terephthalate polyester fibers, such as of 3G-T or 4G-T, for example, and copolyesters. Indeed, the present invention is not limited to polyester fibers, but is believed broadly applicable to synthetic fibers, generally, and especially to those prepared by spinning filaments from a melt of the synthetic polymer, including polyamides, such as nylon 6,6 and nylon 6, polyolefins, such as polypropylene and polyethylene by way of example, but, as will be understood, since the invention was made in the course of melt-spinning polyester filaments, most of the description hereinafter discusses application of the invention to polyester filaments, and especially to bicomponent filaments such as are described and claimed in our previous applications, referred to hereinbefore.
Champaneria et al. U.S. Pat. No. 3,745,061 disclosed synthetic filaments having at least three continuous non-round voids. FIG. 2 of Champaneria is an enlarged sectional view taken from a photomicrograph of a nylon filament spun through an orifice similar to Champanerial's FIG. 1 except for omission of one segment. FIG. 1 of Champaneria represents a spinneret orifice for spinning filaments containing four, substantially equi-dimensional and equi-spaced, parallel continuous voids, such as nylon filaments of cross-section as shown in FIGS. 1a, 1b and 1c of Champaneria. As indicated, all the voids of Champaneria's filaments were "non-round". Champaneria did not illustrate any spinneret orifice for spinning filaments with three voids. The spinneret orifice shown in Champaneria's FIG. 1 was segmented with slot segments and spokes. Such spokes are shown terminating toward the center of the orifice with squared ends. Champaneria did not disclose any filaments with round voids, i.e., of essentially circular cross-section. All the filament cross-sections illustrated by Champaneria in his FIGS. 1a, 1b, 1c, 2 and 3 had the non-round voids desired by Champaneria. Champaneria did not teach how to spin filaments with round voids.